Many Midrashim compare and contrast Noach and Avraham. In fact, Rashi quotes an opinion that if Noach were in the same generation as Avraham, he would not have been considered such a Tzaddik. Some suggest that the reason for this is that Noach did not pray to help the people of his generation, whereas Avraham, placed in a similar situation, prayed for the people of Sedom.
The Kedushat Levi, Reb Levi Yitzchak Miberditchev, explains that there are two types of Tzaddikim. Some serve Hashem wholeheartedly but do not bring others closer to Hashem through their services. Others serve Hashem and are able to bring others who do not act properly closer to Hashem. The Kedushat Levi quotes the Ari Hakadosh, who says that Noach received a punishment because of his inability to bring the people of his generation closer to Hashem. He explains, however, that the reason Noach did not pray for the people of his generation was because he did not view himself so highly. Consequently, he did not feel that his prayers would have any affect on Hashem’s decision to bring the flood.
The Shem Mishmuel might offer another explanation why Noach did not interact with the people around him. Noach’s righteousness was with him from the earliest parts of his life, and his goal in life was to retain this high level. Avraham, however, had to work very hard to attain his high level. Since Noach’s job was to retain his Kedusha, he had to separate himself from the people of his generation. This could be why he did not help those around him repent, whereas Avraham, who knew how to rise in Kedusha, was able to bring many other people closer to Hashem.
The Slonimer Rebbe, zt”l, wrote that there was a fundamental difference between Avraham and Noach: Avraham’s dominant trait was Chessed, and Avraham was closer to Hashem through his אהבה while Noach was closer to Hashem through his יראה. This helps explain the Pasuk, את האלוקים התהלך נח, “Noach walked with Hashem” (6:9). It was אלוקים, the name of Hashem that represents יראה, that was most relevant to Noach. This teaches us an important lesson: one can reach Hashem in a variety of ways: through אהבה or through יראה; as long as we strive to be close to Hashem, everything else will fall into place.